Each workstation is identified in the application program by a unique number, the workstation identifier. This number is used in routines which communicate with the device, i.e. when output is to be sent to it, or when it is to be cleared, etc. In order to establish a connection between the application program and a workstation, the workstation has to be opened. When the workstation is closed, the connection is released, segments stored in Workstation Dependent Segment Storage are lost, and no further interactions are possible.
The calls to open and close a workstation are:
CALL GOPWK(WKID, CONID, WTYPE) and CALL GCLWK(WKID)
The workstation identifier WKID is a positive integer which the application chooses, and is typically a number like 1,2,3... The integer CONID is the Connection Identifier which connects the workstation to an I/O channel. It is usually a FORTRAN logical unit number, but depends on the workstation and the host computer being used. Thus, the value of conid must be obtained from the workstation-dependent documentation.
The Workstation Type (WTYPE) is an integer which specifies which type of workstation should be opened, e.g. a Tektronix 4014 or a Versatec plotter. Workstation Types are implementation dependent. A list of workstation identifiers in use at CERN will be found in the appendix.